1. Field of the Invention
This invention relates to the stabilization of peroxidase conjugates in solution.
2. Description of the Prior Art
Enzyme immunoassay (EIA) provides simple and rapid detection of a variety of antigens, e.g., pathogens, toxins, and environmental pollutants in addition to antibodies for serodiagnosis. In EIA, enzyme conjugates of immunoreactants (antibodies or antigens) are used to quantitate sample immunoreactants by measuring the amounts of enzyme products. Since the enzyme conjugates have limited stability at ambient temperatures, refrigeration is normally required for their transportation and storage. Horseradish peroxidase (HRP) is a popular EIA enzyme because of its low price and high specific activity. HRP is a glycoprotein of relatively high carbohydrate content (e.g., 20%).
HRP is also used in other conjugates. These include HRP-labeled lectins which are useful for the characterization of glycoproteins or carbohydrates-containing substances because of lectins' specific interaction with carbohydrate moieties. HRP-protein A and G are other HRP conjugates which are extensively used in the detection of antibodies because of specific interaction between these proteins and antibodies. HRP-streptavidin or avidin is used to detect any biotin-containing substances because of specific interaction between streptavidin or avidin and biotin.
Since field EIA would facilitate control of pathogens, diseases, and pollutants, it is important to develop methods for stabilizing the activity of enzyme-conjugates at ambient temperatures. For field EIA applications, it is desirable to have a conjugate suspension that can be used without further dilution prior to EIA.